Process for producing porous polymer

ABSTRACT

A method of production is provided which is capable of efficiently producing in a very short period of time a porous polymer possessing a uniform foam structure and truly excelling in absorption properties and physical properties. It is a method for the production of a porous polymer, characterized by comprising (a) an emulsifying step for forming a water-in-oil type high internal phase emulsion (HIPE) by mixing and stirring an oil phase containing a polymerizing monomer component and a surfactant as essential components, (b) a shaping step for shaping the HIPE in a specific form, and (c) a polymerizing step for polymerizing the shaped HIPE and controlling the temperatures of the emulsion at the component steps (a)-(c) so that they may not produce a change exceeding 10° C. or controlling all the component steps so that they may proceed at temperatures of not lower than 80° C.

TECHNICAL FIELD

[0001] This invention, in the production of a porous polymer having opencells form open pores extending from the surface through the interiorthereof by polymerizing a water-in-oil type high internal phase emulsion(hereinafter occasionally abbreviated as “HIPE”), relates to a methodfor producing the porous polymer by curing the HIPE in a very shortperiod of time. More particularly, this invention relates to a methodfor the production of a porous polymer having open cells and proving tobe useful in a wide range of applications including (1) liquid absorbingmaterials such as, for example, (a) absorbing materials for such humoralfluids as urine and blood, typified by cores in disposable diapers and(b) absorbing materials for water, oil, and organic solvents, typifiedby agents for disposing of waste water, waste oil, and waste solvent,(2) energy absorbing materials such as, for example, absorbing materialsfor sound and heat, typified by sound insulators and heat insulators,and (3) bases for impregnation with pharmaceutical preparations such as,for example, household articles impregnated with aromatic agents,cleaning agents, lustering agents, surface protecting agents, and flameretardants.

BACKGROUND ART

[0002] The term HIPE refers to an emulsion having a water phase which isa disperse phase (inner phase) and an oil phase which is an outer phaseat a ratio (W/O ratio) of not less than about 3/1. It has been known toproduce a porous polymer by polymerizing this HIPE. While a porouspolymer which is produced by using a foaming agent without involvingconversion into an HIPE (hereinafter occasionally referred to briefly as“foam”) is liable to afford a foam made up of discrete cells of arelatively large pore diameter, the method for producing a porouspolymer from the HIPE (hereinafter occasionally referred to briefly as“HIPE method”) is an excellent process for the production of a foam oflow density made up of open cells of a minute pore diameter.

[0003] Methods proposed with the object of producing porous polymersfrom an HIPE have been disclosed in JP-A-57-98713, JP-A-62-50002, U.S.Pat. No. 5,252,619, and U.S. Pat. No. 5,189,070, for example.

[0004] JP-A-57-98713 and JP-62-50002 disclose a method which comprisespreparing an HIPE containing a water-soluble and/or an oil-solublepolymerization initiator and thermally polymerizing this HIPE at 50° C.or 60° C. for a period of from 8 hours through 72 hours. U.S. Pat. No.5,210,104 discloses a method which comprises preparing an HIPE andsubsequently adding a polymerization initiator thereto, U.S. Pat. No.5,252,619 discloses a method which comprises preparing an HIPEcontaining a polymerization initiator and then polymerizing the HIPE ata temperature of not lower than 90^(P)C., and U.S. Pat. No. 5,189,070discloses a method which comprises forming a gel possessing a prescribeddynamic shear modulus from an emulsion at a temperature of 20° —lessthan 65° C. and then polymerizing this gel at a temperature of not lowerthan 70° C.

[0005] The methods which are disclosed in JP-A-57-98713 and JP-62-50002,however, require unduly long times for polymerization and suffer fromunsatisfactory efficiency of production. While the methods of U.S. Pat.No. 5,252,619 and U.S. Pat. No. 5,189,070 are capable of completingpolymerization in comparatively short periods of time when thetemperatures used are high, they still require unduly long timesapproximating several hours for polymerization and, depending onconditions, impair the stability of a relevant HIPE, tend to entailliberation of a large quantity of water, and eventually fail to obtain aporous polymer of a prescribed pore diameter. The method of U.S. Pat.No. 5,210,104 is described to require several hours as the time forpolymerization, though it is capable of improving the stability of theemulsification of an HIPE owing to the addition of a polymerizationinitiator subsequently to the preparation of the HIPE.

[0006] We have taken notice of the time required for the polymerizationof an HIPE, pursued a study in search of a method for producing a porouspolymer by polymerizing (curing) an HIPE in a very short period of time,perfected a procedure for fulfilling this method, and filed theinvention covering this method for patent (Japanese Patent ApplicationNo. 290141/1999). Though this procedure has been confirmed to improvemarkedly the factor of the time for polymerization and enhance theproductivity, it has betrayed the possibility of varying the particlediameter of an emulsion and the distribution thereof depending on thekind of emulsion and the conditions of polymerization during the changeof the temperature of the emulsion particularly at a specific rate oftemperature increase and consequently inducing fine variation in theparticle diameter of the produced foam and preventing the form frommanifesting expected foam properties.

[0007] The object of this invention, therefore, comprises solving such atechnical problem as implied above and providing a method for theproduction of a porous polymer which can produce the porous polymer withfurther exalted foam properties such as, for example, the absorptionproperties of foam in a very short period of time such as, for example,not more than 30 minutes and preferably not more than 20 minutes.

DISCLOSURE OF THE INVENTION

[0008] We, as a result of performing a diligent study with a view todeveloping a method for producing a porous polymer from an HIPE in avery short period of time, have discovered that a porous polymerexcelling in foam properties can be produced preferably continuously ina very short period of time such as, for example, not more than 30minutes and preferably not more than 10 minutes in the method for theproduction of a porous polymer which comprises (a) an emulsifying stepfor producing an HIPE, (b) a shaping step for imparting a prescribedshape to the HIPE, and (c) a polymerizing step for polymerizing theformed HIPE, by heeding changes of temperature of the HIPE during thecomponent steps (a)-(c) of the process mentioned above and controllingthe temperature of the emulsion so as not to produce a change exceeding10° C. in the intervals between the component steps of the process or inthe method for the production of a porous polymer which comprises (a) anemulsifying step for preparing an HIPE, (b) a shaping step for impartinga shape to the HIPE, and (c) a polymerizing step for polymerizing thisHIPE, by controlling the temperatures in the component steps of theprocess mentioned above so as to remain in respectively specifiedranges. This invention has been consequently perfected.

[0009] The object mentioned above is accomplished by the following items(1)-(7).

[0010] (1) A method for the production of a porous polymer by thepolymerization of a water-in-oil type high internal phase emulsionobtained from an oil phase containing a polymerizing monomer componentand a surfactant and a water phase containing water, which method ischaracterized by comprising (a) an emulsifying step for forming awater-in-oil type high internal phase emulsion, (b) a shaping step forshaping the emulsion in the form of a sheet or a film, and (c) apolymerizing step for polymerizing the emulsion and having thetemperatures during the component steps mentioned above so controlled asto produce no change exceeding 10° C.

[0011] (2) A method for the production of a porous polymer by thepolymerization of a water-in-oil type high internal phase emulsionobtained from an oil phase containing a polymerizing monomer componentand a surfactant and a water phase containing water, which method ischaracterized by comprising (a) a continuous emulsifying step forcontinuously forming a water-in-oil type high internal phase emulsion,(b) a continuous shaping step for continuously shaping the emulsion inthe form of a sheet or a film, and (c) a continuous polymerizing stepfor continuously polymerizing the emulsion and having the temperaturesduring the component steps mentioned above so controlled as to produceno change exceeding 10° C.

[0012] (3) A method for the production of a porous polymer by thepolymerization of a water-in-oil type high internal phase emulsionobtained from an oil phase containing a polymerizing monomer componentand a surfactant and a water phase containing water, which method ischaracterized by comprising (a) a continuous emulsifying step forcontinuously forming a water-in-oil type high internal phase emulsion,(b) a continuous shaping step for continuously shaping the emulsion in athickness of not more than 50 mm, and (c) a continuous polymerizing stepfor continuously polymerizing the emulsion and having the temperaturesduring the component steps mentioned above so controlled as to produceno change exceeding 10° C.

[0013] (4) A method for the production of a porous polymer by thepolymerization of a water-in-oil type high internal phase emulsionobtained from an oil phase containing a polymerizing monomer componentand a surfactant and a water phase containing water, which method ischaracterized by comprising (a) an emulsifying step for forming awater-in-oil type high internal phase emulsion, (b) a shaping step forshaping the emulsion in the form of a sheet or a film, and (c) apolymerizing step for polymerizing the emulsion and having the componentsteps of the process mentioned above to proceed invariably at atemperature of not lower than 80° C. and not higher than 110° C.

[0014] (5) A method for the production of a porous polymer by thepolymerization of a water-in-oil type high internal phase emulsionobtained from an oil phase containing a polymerizing monomer componentand a surfactant and a water phase containing water, which method ischaracterized by comprising (a) a continuous emulsifying step forcontinuously forming a water-in-oil type high internal phase emulsion,(b) a continuous shaping step for continuously shaping the emulsion inthe form of a sheet or a film, and (c) a continuous polymerizing stepfor continuously polymerizing the emulsion and having the componentsteps of the process mentioned above to proceed invariably at atemperature of not lower than 80° C. and not higher than 110° C.

[0015] (6) A method for the production of a porous polymer by thepolymerization of a water-in-oil type high internal phase emulsionobtained from an oil phase containing a polymerizing monomer componentand a surfactant and a water phase containing water, which method ischaracterized by comprising (a) a continuous emulsifying step forcontinuously forming a water-in-oil type high internal phase emulsion,(b) a continuous shaping step for continuously shaping the emulsion in athickness of not more than 50 mm, and (c) a continuous polymerizing stepfor continuously polymerizing the emulsion and having the componentsteps of the process mentioned above to proceed invariably at atemperature of not lower than 80° C. and not higher than 110° C.

[0016] (7) A method for the production of a porous polymer by thepolymerization of a water-in-oil type high internal phase emulsionobtained from an oil phase containing a polymerizing monomer componentand a surfactant and a water phase containing water, which method ischaracterized by comprising (a) a continuous emulsifying step forcontinuously forming a water-in-oil type high internal phase emulsion,(b) a continuous shaping step for continuously shaping the emulsion in anecessary shape, and (c) a continuous polymerizing step for continuouslypolymerizing the emulsion and having the component steps of the processmentioned above to proceed invariably at a temperature of not lower than80° C. and having a polymerization initiator incorporated in theemulsion after the start of (a) the continous emulsifying step andbefore the completion of (b) the continuous shaping step.

BEST MODE FOR CARRYING OUT THE INVENTION

[0017] [I] For a start, the steps of process in the first, second, andthird methods of production according to this invention will bedescribed in detail below in the order of their occurrence.

[0018] The first aspect of this invention is directed toward a methodfor the production of a porous polymer by the polymerization of awater-in-oil type high internal phase emulsion obtained from an oilphase containing a polymerizing monomer component and a surfactant and awater phase containing water, which method is characterized bycomprising (a) an emulsifying step for forming a water-in-oil type highinternal phase emulsion, (b) a shaping step for shaping the emulsion inthe form of a sheet or a film, and (c) a polymerizing step forpolymerizing the emulsion and having the temperatures during thecomponent steps mentioned above so controlled as to produce no changeexceeding 10° C.

[0019] The second aspect of this invention is directed toward a methodfor the production of a porous polymer by the polymerization of awater-in-oil type high internal phase emulsion obtained from an oilphase containing a polymerizing monomer component and a surfactant and awater phase containing water, which method is characterized bycomprising (a) a continuous emulsifying step for continuously forming awater-in-oil type high internal phase emulsion, (b) a continuous shapingstep for continuously shaping the emulsion in the form of a sheet or afilm, and (c) a continuous polymerizing step for continuouslypolymerizing the emulsion and having the temperatures during thecomponent steps mentioned above so controlled as to produce no changeexceeding 10° C.

[0020] The third aspect of this invention is directed toward a methodfor the production of a porous polymer by the polymerization of awater-in-oil type high internal phase emulsion obtained from an oilphase containing a polymerizing monomer component and a surfactant and awater phase containing water, which method is characterized bycomprising (a) a continuous emulsifying step for continuously forming awater-in-oil type high internal phase emulsion, (b) a continuous shapingstep for continuously shaping the emulsion in a thickness of not morethan 50 mm, and (c) a continuous polymerizing step for continuouslypolymerizing the emulsion and having the temperatures during thecomponent steps mentioned above so controlled as to produce no changeexceeding 10° C.

[0021] (a) Emulsifying Step to form Water-In-Oil Type High InternalPhase Emulsion (HIPE)

[0022] 1. Raw Materials to be used for HIPE

[0023] The raw materials to be used for the HIPE are an oil phasecontaining (1) a polymerizable monomer component and (2) a surfactantand a water phase containing (3) water. As typical examples of thepolymerizable monomer component, (1-1) polymerizing monomers which haveone polymerizable unsaturated group in the molecular unit thereof and(1-2) cross-linkable monomers which have at least two polymerizableunsaturated groups in the molecular unit thereof may be cited. The rawmaterials, when necessary, may further include (4) a polymerizationinitiator, (5) a salt, and (6) other additive as arbitrary componentsfor the oil phase and/or the water phase.

[0024] (1) Polymerizable Monomer Component

[0025] The polymerizable monomer component is capable of forming across-linked structure by polymerization and generally comprises (1-1) apolymerizing monomer having one polymerizable unsaturated group in themolecular unit thereof and/or (1-2) a cross-linkable monomer having atleast two polymerizable unsaturated groups in the molecular unitthereof. They do not need to be particularly restricted but are onlyrequired to be capable of being dispersed or polymerized in awater-in-oil type high internal phase emulsion so as to give rise to afoam.

[0026] The polymerizable monomer (1-1) preferably contains a(meth)acrylic ester at least partly, more preferably contains not lessthan 20 mass % of a (meth)acrylic ester, and particularly preferablycontains not less than 35 mass % of a(meth)acrylic acid. The fact thatthe polymerizable monomer (1-1) contains a (meth)acrylic ester is at anadvantage in enabling production of a porous polymer which abounds insoftness and toughness.

[0027] As typical examples of the polymerizable monomer (1-1), arylenemonomers such as styrene; monoalkylene arylene monomers such as styrene,ethyl styrene, alpha methyl styrene, vinyl toluene, and vinyl ethylbenzene; (meth)acrylic esters such as methyl (meth)acrylate, ethyl(meth)acrylate, butyl (meth)acrylate, isobutyl (meth)acrylate, isodecyl(meth)acrylate, 2-ethylhexyl(meth)acrylate, lauryl (meth)acrylate,stearyl (meth)acrylate, cyclohexyl (meth)acrylate, and benzyl(meth)acrylate; chlorine-containing monomers such as vinyl chloride,vinylidene chloride, and chloromethyl styrene; acrylonitrile compoundssuch as acrylonitrile and methacrylonitrile; and other compounds such asvinyl acetate, vinyl propionate, N-octadecyl acrylamide, ethylene,propylene, and butene may be cited. Besides being used singly, thesepolymerizing monomers may be used in the form of a combination of two ormore members.

[0028] The quantity of the polymerizable monomer (1-1) to be usedgenerally is preferred to be in the range of 10-99.9 mass %, based onthe weight of the whole polymerizable monomer which comprises thepolymerizable monomer (1-1) mentioned above and the cross-linkablemonomer (1-2) which will be specifically described herein below. Whenthe quantity is in this range, the produced porous polymer acquires afine pore diameter. The quantity is preferably in the range of 30-99mass % and particularly preferably in the range of 50-95 mass %. If thequantity of the polymerizable monomer (1-1) to be used falls short of 10mass %, the shortage will possibly render the produced porous polymerunduly brittle or deficient in the ratio of water absorption.Conversely, if the quantity of the polymerizable monomer (1-1) to beused exceeds 99.9 mass %, the excess will possibly render the producedporous polymer deficient in strength and power of elastic recovery andincapable of absorbing water in a fully satisfactory amount at asatisfactory speed.

[0029] The cross-linking monomer (1-2) mentioned above has only tocontain at least two polymerizable unsaturated groups in the molecularunit thereof and permit formation of a cross-linked structure bypolymerization. Similarly to the polymerizable monomer (1-1) mentionedabove, it does not need to be particularly restricted but is onlyrequired to be dispersible or polymerizable in a water-in-oil type highinternal phase emulsion so as to give rise to a foam.

[0030] As typical examples of the cross-linkable monomer (1-2), aromaticmonomers such as divinyl benzene, trivinyl benzene, divinyl toluene,divinyl xylene, p-ethyl-vinyl benzene, divinyl naphthalene, divinylalkyl benzenes, divinyl phenanthrene, divinyl biphenyl, divinyl diphenylmethane, divinyl benzyl, divinyl phenyl ether, and divinyl diphenylsulfide; oxygen-containing monomers such as divinyl furan;sulfur-containing monomers such as divinyl sulfide and divinyl sulfone;aliphatic monomers such as butadiene, isoprene, and pentadiene; andesters of polyhydric alcohols with methacrylic acid or methacrylic acidsuch as ethylene glycol di(meth)acrylate, diethylene glycoldi(meth)acrylate, triethylene glycol di(meth)acrylate, polyethyleneglycol di(meth)acrylate, 1,3-butane diol di(meth)acrylate, 1,4-butanediol di(meth)acrylate, 1,6-hexane diol di(meth)acrylate, octane dioldi(meth)acrylate, decane diol di(meth)acrylate, trimethylol propanedi(meth)acrylate, trimethylol propane tri(meth)acrylate, pentaerythritoldi(meth)acrylate, penta-erythritol tri(meth)acrylate, pentaerythritoltetra(meth)acrylate, dipentaerythritol di(meth)acrylate,dipentaerythriol tri(meth)acrylate, dipentaerythritoltetra(meth)acrylate, N,N′-methylene bis(meth)-acrylamide, triallylisocyanurate, triallyl amine, tetralloloxy ethane, hydroquinone,catechol, resorcinol, and sorbitol may be cited. These cross-linkablemonomers may be used in the form of a combination of two or more membersbesides being used singly.

[0031] The quantity of the cross-linkable monomer (1-2) mentioned aboveis preferably in the range of 0.1-90 mass %, more preferably in therange of 1-70 mass %, and particularly preferably in the range of 5-50mass %, based on the weight of the whole polymerizable monomer componentwhich comprises the polymerizable monomer (1-1) and the cross-linkablemonomer (1-2). If the quantity of the cross-linkable monomer (1-2) to beused falls short of 0.1 mass %, the shortage will possibly render theproduced porous polymer unduly deficient in strength and power ofelastic recovery, insufficient in capacity for absorption per unitvolume or unit weight, and incapable of absorbing water in a fullysatisfactory amount at a satisfactory speed. Conversely, if the quantityof the cross-linkable monomer (1-2) to be used exceeds 90 mass %, theexcess will possible render the porous polymer unduly brittle orinsufficient in the ratio of cubital expansion due to absorption ofwater.

[0032] (2) Surfactant

[0033] The surfactant mentioned above does not need to be particularlyrestricted but is only required to be capable of emulsifying the waterphase in the oil phase forming the HIPE. It may be selected from amongnonionic surfactants, cationic surfactants, anionic surfactants, andamphoteric surfactants which have been heretofore known to the art.

[0034] As typical examples of the nonionic surfactant, nonylphenolpolyethylene oxide adduct; block polymer of ethylene oxide withpropylene oxide; sorbitan fatty acid esters such as sorbitanmonolaurate, sorbitan monomyristylate, sorbitan monopalmitate, sorbitanmonostearate, sorbitan tristearate, sorbitan monooleate, sorbitantrioleate, sorbitane sesquioleate, and sorbitan distearate; glycerinfatty acid esters such as glycerol monostearate, glycerol monooleate,diglycerol monooleate, and self-emulsifying glycerol monostearate;polyoxyethylene alkyl ethers such as polyoxyethylene lauryl ether,polyoxyethylene cetyl ether, polyoxyethylene stearyl ether,polyoxyethylene oleyl ether, and polyoxyethylene higher alcohol ethers;polypoxyethylene alkylaryl ethers such as polyoxyethylene nonylphenylether; polyoxyethylene sorbitan fatty acid esters such aspolyoxyethylene sorbitan monolaurate, polyoxyethylene sorbitanmonopalmitate, polyoxyethylene sorbitan monostearate, polyoxyethylenesorbitan tristearate, polyoxyethylene sorbitan monooleate, andpolyoxyethylene sorbitan trioleate; polyoxyethylene sorbitol fatty acidesters such as tetraoleic acid polyoxyethylene sorbit; polyoxyethylenefatty acid esters such as polyethylene glycol monolaurate, polyethyleneglycol monostearate, polyethylene glycol distearate, and polyethyleneglycol monooleate; polyoxyethylene alkyl amines; polyoxyethylene-curedcastor oil; and alkyl alkanol amides may be cited. Particularly, the HLBvalues of these nonionic surfactants are not more than 10 and preferably2-6. These nonionic surfactants may be used in the form of a combinationof two or more members. This combined use possibly results in improvingthe HIPE in stability.

[0035] As typical examples of the cationic surfactant, quaternaryammonium salts such as stearyl trimethyl ammonium chloride, ditallowdimethyl ammonium methyl sulfate, cetyl trimethyl ammonium chloride,distearyl dimethyl ammonium chloride, and alkyl benzyl dimethyl ammoniumchloride; alkyl amine salts such as coconut amine acetate and stearylamine acetate; alkyl betaines lauryl trimethyl ammonium chloride, laurylbetaqine, stearyl betaine, and lauryl carboxymethyl hydroxyethylimidazolinium betaine; and amine oxides such as lauryl dimethyl amineoxide may be cited. By adding such a cationic surfactant, it may be madepossible to impart to the produced porous polymer an excellentantibacterial property when the porous polymer is used inwater-absorbing materials.

[0036] Incidentally, the combined use of a nonionic surfactant and acationic surfactant possibly results in imparting improved stability tothe HIPE.

[0037] The quantity of the surfactant mentioned above to be used ispreferably in the range of 1-30 mass parts and more preferably in therange of 3-15 mass parts, based on 100 mass parts of the wholepolymerizable monomer component which comprises a polymerizable monomer(1-1) and a cross-linkable monomer (1-2). If the quantity of thesurfactant to be used falls short of 1 mass part, the shortage willpossible result in destabilizing the HIPE in dispersibility andpreventing the surfactant from fully satisfactorily manifesting theaction and effect inherent therein. Conversely, if the quantity of thesurfactant to be used exceeds 30 mass parts, the excess will be at adisadvantage economically in possibly rendering the produced porouspolymer unduly brittle and failing to bring about a proportionateaddition to the effect to be manifested.

[0038] (3) Water

[0039] As the water mentioned above, the waste water which occurs in theproduction of the porous polymer may be used either directly or afterundergoing a prescribed treatment, besides the tap water, purifiedwater, and deionized water.

[0040] The quantity of the water mentioned above to be used can besuitably selected, depending on the purpose for which the porous polymerhaving an open cell is to be used (such as, for example, awater-absorbing material, an oil-absorbing material, a sound insulator,or a filter). Since the hole ratio of a porous polymer is decided byvarying the water phase/oil phase (W/O) ratio of a given HIPE, thequantity of the water to be used is automatically decided by selectingsuch a W/O ratio as conforms to the hole ratio which fits the purpose ofuse mentioned above.

[0041] (4) Polymerization Initiator

[0042] For the purpose of accomplishing the polymerization of an HIPE ina very short period of time as aimed at by this invention, it ispreferable to use a polymerization initiator. This polymerizationinitiator is only required to be usable in ordinary polymerization. Itmay be soluble in water or in oil, whichever fits the occasion better.

[0043] As concrete examples of the water-soluble polymerizationinitiator, azo compounds such as 2,2′-azobis-(2-amidinopropane)dihydrochloride; persulfates such as ammonium persulfate, potassiumpersulfate, and sodium persulfate; and peroxides such as potassiumperacetate, sodium peracetate, potassium percarbonate, and sodiumpercarbonate may be cited.

[0044] As typical examples of the oil-soluble polymerization initiator,hydroperoxides such as cumene hydroperoxide, t-butyl hydroperoxide,diisopropyl benzene hydroperoxide, p-menthane hydroperoxide, and1,1,3,3-tetramethyl butyl hydroperoxide; dialkyl peroxides such asdi-t-butyl peroxide, 2,5-dimethyl-2,5-di(t-butyl peroxy) hexane, tbutylcumyl peroxide, and dicumyl peroxide; peroxy carbonates such asdi-isopropyl peroxy dicarbonate, dicyclohexyl peroxy dicarbonate,di(s-butyl) peroxy dicarbonate, and di(2-ethylhexyl) peroxy dicarbonate;diacyl peroxides such as acetyl peroxide, propionyl peroxide, decanoylperoxide, isobutylyl peroxide, octanoyl peroxide, lauroyl peroxide,stearolyl peroxide, and benzoyl peroxide; peroxy ketals such as1,1′-di-(t-butyl peroxy) cyclohexane and 1,1′-di-(t-butylperoxy)-3,3,5-trimethyl cyclohexane; ketone peroxides such ascyclohexanone peroxide, methyl cyclohexanon peroxide, methylethyl ketoneperoxide, and acetyl acetone peroxide; and peroxy esters such as cumylperoxy neodecanoate, 1,1,3,3-tetramethylbutyl peroxy neodecanoate,1-cyclohexyl-1-1-methylethyl peroxy neodecanoate, t-hexylperoxyneodecanoate, t-butyl peroxy neodecanoaate, t-butyl peroxy isobutyrate,t-butyl peroxy pivalate, 1,1,2,2-tetramethylbutyl peroxy-2-ethylhexanoate, 2,5-dimethyl-2,5-di(2-ethylhexanoyl peroxy) hexane,1-cyclohexyl-1-1-methylethyl peroxy-2-hexanoate, t-amyl peroxy2-ethylhexanoate, and t-butyl peroxy 2-ethyl hexanoate may be cited.

[0045] These polymerization initiators may be used either singly or inthe form of a combination of two or more members. As a matter of course,it is permissible to use a water-soluble polymerization initiator and anoil-soluble polymerization initiator in combination.

[0046] The quantity of a polymerization initiator which can be used inthe reversed-phase emulsion polymerization is preferably in the range of0.05-25 mass parts and more preferably in the range of 1.0-10 massparts, based on 100 mass parts of the whole polymerizable monomercomponent comprising a polymerizable monomer (1-1) and a cross-linkablemonomer (1-2), though depending on the combination of the polymerizablemonomer component and a polymerization initiator. If the quantity of thepolymerization initiator to be used falls short of 0.05 mass part, theshortage will be at a disadvantage in increasing the amount of anunaltered polymerizing monomer component and consequently adding to theamount of a residual monomer in the produced porous polymer. Conversely,if the quantity of the polymerization initiator to be used exceeds 25mass parts, the excess will be at a disadvantage in rendering thecontrol of polymerization difficult and degrading the mechanicalproperty of the produced porous polymer.

[0047] It is further permissible to use a redox polymerization initiatorsystem which is formed by the combination of the polymerizationinitiator mentioned above with a reducing agent. The polymerizationinitiator in this system may be soluble in water or in oil, which eversuits the occasion better. It is permissible to use a water-solubleredox polymerization initiator system and an oil-soluble redoxpolymerization initiator system in combination. As typical examples ofthe water-soluble reducing agent, sodium hydrogen sulfite, potassiumhydrogen sulfite, sodium thiosulfate, potassium thiosulfate, L-ascorbicacid, erysorbic acid, ferrous salts, formaldehyde sodium sulfoxylate,glucose, dextrose, triethanol amine, and diethanol amine may be cited.As typical examples of the oil-soluble reducing agent, such compounds asdimethyl aniline may be cited. These reducing agents in the redoxpolymerization initiator may be used either singly or in the form of acombination of two or more members. In the case of the redoxpolymerization initiator system, the ratio of the reducing agent (bymass) to be contained therein is such that the polymerization initiator(oxidizing agent)/reducing agent ratio is approximately in the range of1/0.01-1/10 and preferably in the range of 1/0.2-1/5.

[0048] The polymerization initiator (inclusive of the redoxpolymerization initiator system) mentioned above is only required to bepresent at least during the polymerization of an HIPE. As regards themethod of adding this polymerization initiator which will be describedmore specifically herein below, {circle over (1)} the addition may bemade to the oil phase and/or the water phase in advance of the formationof an HIPE, {circle over (2)} the addition may be made at the same timeas an HIPE is formed, or {circle over (3)} the addition may be madeafter the formation of an HIPE. Then, in the case of the redoxpolymerization initiator system, it is permissible to add thepolymerization initiator (oxidizing agent) and a reducing agent atseparate times.

[0049] (5) Salt

[0050] The salt mentioned above may be used when it is required for thepurpose of imparting improved stability to the HIPE.

[0051] As typical examples of the salt, such water-soluble salts ashalides, sulfates, and nitrates of alkali metals and alkaline earthmetals like calcium chloride, sodium sulfate, sodium chloride, andmagnesium sulfate may be cited. These salts may be used either singly orin the form of a combination of two or more members. Such a salt ispreferred to be added to the water phase. Among other metal salts, apolyvalent metal salt proves particularly preferable from the viewpointof the stability of the relevant HIPE during the course ofpolymerization.

[0052] The quantity of the salt to be used is preferably in the range of0.1-20 mass parts and more preferably in the range of 0.5-10 mass parts,based on 100 mass parts of water. If the quantity of the salt to be usedexceeds 20 mass parts, the excess will be at a disadvantage economicallyin inducing inclusion of a large amount of a salt in the waste watersqueezed from the HIPE and failing to bring about a proportionateaddition to the effect of addition. Conversely, if the quantity of thesalt to be used falls short of 0.1 mass part, the shortage will possiblyprevent the function and effect of the addition of salt from beingmanifested fully satisfactorily.

[0053] (6) Other Additive

[0054] Varyious other additives may be suitably used when the additionof performances and functions owned thereby contributes to theenhancement of the conditions of production, the characteristicproperties of the relevant HIPE, and the performance of the producedporous polymer. A base and/or a buffer agent, for example, may be addedfor the purpose of adjusting the pH. The quantities of such additives tobe used may be suitably selected in the respective ranges in which theadditives are allowed to manifest fully satisfactorily the performancesand functions commensurate with their purposes of addition and satisfyeconomy as well. As typical examples of the additive, activated carbon,inorganic powder, organic powder, metal powder, deodorant, antibacterialagent, mildew proofing agent, perfume, and various high polymers, andsurfactant may be cited.

[0055] 2. Formation (Emulsification) of HIPE

[0056] The method which can be used in this invention for the formation(emulsification) of an HIPE does not need to be particularly restricted.Any of the heretofore known methods of preparing an HIPE may be suitablyutilized. The typical method of preparing an HIPE will be specificallydescribed below.

[0057] For a start, the components forming an oil phase which comprisesa polymerizable monomer and a surfactant, a polymerization initiator(inclusive of redox polymerization initiator) further incorporatedoptionally therein, and other additives in respective quantitiesspecified above are stirred at a prescribed temperature to prepare ahomogeneous oil phase.

[0058] Separately, the components forming a water phase which compriseswater, a polymerization initiator (inclusive of redox polymerizationinhibitor) further incorporated optionally therein, a salt, and otheradditives in respective quantities specified above are stirred andheated to a prescribed HIPE temperature to prepare a homogeneous waterphase.

[0059] Then, the oil phase which is the mixture of the polymerizablemonomer component, the surfactant, etc. prepared as described above andthe water phase which is the mixture of water, the water-soluble salt,etc. are efficiently mixed and stirred together at the HIPE formingtemperature (emulsifying temperature) which will be specificallydescribed below and emulsified under the optimal shearing force toaccomplish stable preparation of an HIPE. As the means of stirring andmixing the water phase and the oil phase for the stable preparation ofan HIPE, it is preferable to adopt the method which comprises keepingthe oil phase stirred and continuously adding the water phase to thestirred oil phase over a period ranging from several seconds throughsome tens of minutes. Otherwise, the HIPE aimed at may be produced bystirring and mixing part of the water phase component with the oil phasecomponent till an HIPE is formed and then continuing the stirring andmixing while adding the remainder of the water phase component thereto.For the continuous production contemplated by this invention, the methodwhich comprises continuously feeding the water phase and the oil phasefurther to the HIPE which has been formed by the preceding procedure andcontinuing the formation of the HIPE under a shearing force ispreferably employed.

[0060] 3. Water Phase/Oil Phase (W/O) Ratio

[0061] The water phase/oil phase (W/O) ratio (by mass) of the HIPEobtained as described above does not need to be particularly restrictedbut may be suitably selected depending on the purpose of use (such as,for example, water absorbing material, oil absorbing material, soundinsulator, or filter) to which the porous polymer furnished with an opencell is put. As specified above, this ratio exceeds 3/1 properly andfalls preferably in the range of 10/1-250/1 and particularly in therange of 10/0-100/1. If the W/O ratio falls short of 3/1, the shortagewill possibly render the produced porous polymer insufficient in theability to absorb water and energy and deficient in the numericalaperture as well, compelling the porous polymer to acquire an unduly lownumerical aperture in the surface, and preventing the porous polymerfrom acquiring a fully satisfactory fluid passing property. The holeratio of the porous polymer is decided by selecting the W/O ratio. Itis, therefore, preferable to select the W/O ratio so as to conform tothe hole ratio which fits the purpose of use of the porous polymer. Whenthe porous polymer is used as a varyious absorbent material such as, forexample, a disposable diaper or a sanitary article, it is preferable tofix the W/O ratio at a level in the approximate range of 10/1-100/1. TheHIPE which is obtained by stirring and mixing the water phase and theoil phase is generally a white emulsion of high viscosity. Optionally,it may have the state thereof altered by the composition which varieswith the characteristic property of the foam expected to be obtained.

[0062] 4. Apparatus for Production of HIPE

[0063] The apparatus to be employed for the production of the HIPEmentioned above does not need to be particularly restricted but may beselected from among the heretofore known apparatuses available for theproduction. The stirrer (emulsifier) to be used for the purpose ofmixing and stirring the water phase and the oil phase, for example, maybe selected from among the known stirring devices and kneading devices.As typical examples of the stirrer, stirring devices with propellertype, paddle type, and turbine type vanes, homomixers, pin mixers, linemixers, and static mixers may be cited. These mixers may be used eithersingly or in the form of a combination of two or more members so as toimpart a necessary pore diameter to the HIPE to be formed.

[0064] 5. HIPE Forming Temperature T₀

[0065] The HIPE forming temperature (emulsifying temperature) T₀ at theemulsifying step for forming (a) the water-in-oil type high internalphase emulsion generally is in the range of 40°-110° C. If this T₀ fallsshort of 40° C., the shortage will possibly result in elongating thetime required for the curing. Conversely if the T₀ exceeds 110° C., theexcess will possibly result in rendering the formed HIPE deficient inuniformity. Since this invention requires to maintain the temperature T₀of the HIPE so obtained, keep the change of temperature of the emulsionwithin 10° C., and meanwhile carry out the subsequent (b) shaping stepfor imparting a necessary shape to the emulsion and (c) polymerizingstep for polymerizing the formed emulsion, the HIPE forming temperatureT₀ is preferred to be as high as permissible from the viewpoint ofreducing the time required for the polymerization. It is approximatelyin the range of 60° C.-105° C. and preferably in the range of 80°C.-100° C., for example. The formation of an HIPE having such a hightemperature as exceeds preferably 60° C. and more preferably 80° C. ispreferably accomplished by preparatorily adjusting the temperature ofthe oil phase and/or the water phase at a prescribed HIPE formingtemperature (emulsifying temperature) and then proceeding to stir andmix these two phases. Since the HIPE generally contains the water phasein a larger proportion, however, it may well be rated commendable tohave at least the temperature of the water phase preparatorily adjustedin the neighborhood of the prescribed HIPE forming temperature T₀.

[0066] When the polymerizing monomer component in process ofemulsification begins to polymerize and forms a polymer, thepolymerization possibly destabilizes the HIPE. When the HIPE to beadjusted has preparatorily contained therein a polymerization initiator(inclusive of a redox polymerization initiator system), the HIPE formingtemperature T₀ ought to pay more consideration to the temperature of thepolymerization initiator (oxidizing agent) whose half life is 10 hours(10 hours' half life temperature). When the polymerization initiator isadded at the same time as the HIPE is prepared or after the HIPE hasbeen prepared, the method of mixing the HIPE with the polymerizationinitiator must be selected so as to not only fulfill the 10 hours' halflife temperature but also allow the polymerization inhibitor to beuniformly incorporated fully satisfactorily into the HIPE.

[0067] 6. Method of Adding Polymerization Inhibitor to HIPE

[0068] As typical examples of the way of adding the polymerizationinhibitor to the HIPE, (a) a method which comprises adding thepolymerization initiator to the water phase and/or the oil phase andmixing them in advance of the formation of an HIPE, (b) a method whichcomprises adding and mixing the polymerization initiator with the twophases at the same time as an HIPE is formed, and (c) a method whichcomprises adding the polymerization inhibitor after the formation of anHIPE may be cited. Optionally, these methods may be suitably combined.Even when the polymerization initiator happens to be a redoxpolymerization initiator system or when the polymerization initiator(oxidizing agent) is added in combination with a reducing agent, themethods (a)-(c) mentioned above are available for arbitrary selection.

[0069] In the case of the method of (a), though it is convenient to havethe polymerization initiator or the reducing agent added preparatorilyto the oil phase when it is soluble in water or to the water phase whenit is soluble in water, a method of adding the emulsion of anoil-soluble polymerization initiator (oxidizing agent) or a reducingagent to the water phase may be employed, for example. Thepolymerization initiator can be used in an undiluted state or in theform of a solution or a dispersion in water or an organic solvent.

[0070] In this invention, since the change of temperature of thewater-in-oil type high internal phase emulsion during each of the stepsbetween the time the water-in-oil type high internal phase emulsion isformed and the time the polymerization is completed is small, thepolymerizing monomer component in process of emulsification possiblybegins to polymerize and forms a polymer, depending on the kind ofpolymerization initiator or the method of addition thereof when thetemperature of emulsification is set at a high level of not lower than80° C., for example. For the sake of avoiding this polymerization, it iscommendable to add the polymerization initiator by the method of (b) or(c) mentioned above or add either of the reducing agent and theoxidizing agent (polymerization inhibitor) in the redox initiator systemby the method of (b) or (c) mentioned above.

[0071] When the polymerization inhibitor is added by the method of (b)or (c) as described above at the same time as the HIPE is formed orafter the HIPE has been formed, it is important that the addedpolymerization initiator be uniformly mixed with the HIPE promptly witha view to preventing the polymerizing monomer component from beingununiformly polymerized. In this invention, the HIPE having incorporatedtherein the polymerization initiator is shaped in the form of a sheet ora film or in a thickness of not more than 50 mm and, at the subsequentpolymerizing step, introduced into a polymerization vessel or acontinuous polymerizing device. From this point of view, a method ofadding the polymerization initiator to the HIPE via an inlet portdisposed in the path leading to the site of completion of the shapingstep and continuously mixing them with such a line mixer as a staticmixer is advantageously used.

[0072] The quantity of the polymerization initiator to be used herein isthe same as has been described in the paragraph (4) dealing with thepolymerization initiator of the preceding section 1.covering the rawmaterials to be used for the HIPE.

[0073] (b) Shaping Step for Imparting a Necessary Shape to Water-In-OilType High Internal Phase Emulsion

[0074] 1. HIPE Shaping Temperature T₁

[0075] The HIPE which has incorporated therein a polymerizationinitiator is shaped in a necessary form. The temperature for the shapingof this HIPE is generally in the range of 40°-110° C. This inventionrequires to control the temperature T₁ during the HIPE shaping step sothat the temperature of the HIPE during this step may not produce achange exceeding 10° C. relative to the temperature T₀ during theemulsifying step (a) for forming an HIPE.

[0076] That is, this shaping temperature T₁ is controlled in the rangeof not more than 10° C. from the HIPE forming temperature T₀. If theHIPE shaping temperature T₁ produces a difference exceeding 10° C. fromthe HIPE forming temperature T₀, the excess will be at a disadvantage indelicately varying the uniformity of the emulsion during the formingstep, degrading the properties expected of the finished product, andunduly elongating the time required for the polymerizing step. Thischange of temperature (difference of temperature) is preferably within5° C. and more preferably within 2° C.

[0077] For the purpose of controlling the HIPE shaping temperature T₁lest the temperature of the HIPE should produce a change exceeding 10°C. relative to the HIPE forming temperature T₀, it is necessary that theHIPE conveying line comprising a piping, a line mixer, etc. andextending from the start of the HIPE formation through the shaping stepbe heated and insulated and the shaping vessel be heated and insulatedfully satisfactorily. The time required for imparting a necessary shapeis preferred to be so short that it may be preferably within 5 minutes,more preferably within 3 minutes, and most preferably within 1 minute.Even after the shaping step, the process of production is preferred toadvance quickly to the polymerizing step for the sake of avoiding thechange of temperature during the conveyance to the polymerizing step.The time required in this case is likewise preferred to be so short thatit may be preferably within 5 minutes, more preferably within 3 minutes,and most preferably within 1 minute. When the conditions mentioned aboveare satisfied, the HIPE shaping temperature T₁ is preferred to be ratherhigher than otherwise so as to fall in the approximate range of 60°-105°C. and more advantageously in the range of 80°-100° C.

[0078] 2. Form in which HIPE is Shaped

[0079] In the first and second methods of production contemplated bythis invention, the HIPE is shaped in the form of a sheet or a film. Theform of a sheet and the form of a film are discriminated by rating theshaped HIPE having a thickness of less than 0.25 mm as a film and theshaped HIPE having a thickness of not less than 0.25 mm as a sheet. Thisshaping may be carried out continuously or intermittently. When the HIPEis shaped in such a comparatively thin form as a sheet or a film ascontemplated by this invention, the temperature of the HIPE largelychanges particularly in the course of an ordinary procedure. Thisexplains why this invention requires the conveying line, shaping vessel,and shaping line for the HIPE to be heated and insulated fullysatisfactorily so as to control the change of temperature during thecourse of the shaping within 10° C. relative to the HIPE formingtemperature T₀.

[0080] When the HIPE is shaped in the form of a sheet, the thickness ofthis sheet is irrelevant. An excess of this thickness over 50 mm,however, demands due attention because it possibly results in inducingdeflective separation of the oil phase and the water phase of the HIPEin the vertical direction and impairing the uniformity of composition ofthe HIPE, depending on the kind of HIPE, preventing the whole HIPE frombeing uniformly polymerized, depriving the properties of the porouspolymer of uniformity, preventing the HIPE in process of shaping frombeing fully satisfactorily heated and insulated, and aggravating thechange of temperature. The thickness is preferably not more than 30 mm,more preferably not more than 15 mm, particularly preferably not morethan 10 mm, and most preferably not more than 5 mm. The form of acontinuous sheet or film and the form of an intermittent sheet or filmwhich have a thickness in the range specified above can be usedadvantageously for this invention. The term “thickness” as used hereinrefers to the distance from one surface to the other surface of a givenobject and, when an HIPE is externally heated, for example, means thedistance (wall thickness) of the HIPE in the perpendicular directionrelative to the surface of the HIPE being heated.

[0081] In the third method of production according to this invention, anHIPE is shaped in a thickness of not more than 50 mm. If this thicknessexceeds 50 mm, the excess will possibly result in inducing deflectiveseparation of the oil phase and the water phase of the HIPE in thevertical direction and impairing the uniformity of composition of theHIPE, depending on the kind of HIPE, preventing the whole HIPE frombeing uniformly polymerized, and depriving the properties of the porouspolymer of uniformity. When the shaping is made in such a comparativelysmall thickness as mentioned above, however, the temperature of the HIPEis similarly liable to change largely. This invention controls thischange of temperature within 10° C. relative to the HIPE formingtemperature T₀ in the same manner as is described above, specifically byheating and insulating fully satisfactorily the conveying line, shapingvessel, and shaping line for the HIPE. Approximately, the thickness ofshaping of the HIPE is preferably not more than 30 mm, more preferablynot more than 15 mm, particularly preferably not more than 10 mm, andmost preferably not more than 5 mm. The lower limit of the thickness ofshaping of the HIPE does not need to be particularly restricted but maybe properly decided to suit the purpose of use of the product. Even whenthe produced porous polymer has a small thickness, by using a pluralityof such porous polymers in a superposed state as in a liquid absorbingmaterial, an energy absorbing material, or a chemical impregnatingmaterial, for example, it is made possible to secure the performance andquality which are expected of the material. When the porous polymer hasa thickness of less than 0.1 mm, it demands payment of due heed becauseit possibly renders the handling thereof difficult.

[0082] (c) Polymerizing Step for Polymerizing Water-In-Oil Type HighInternal Phase Emulsion (HIPE)

[0083] 1. Method of Polymerizing HIPE

[0084] Now, the HIPE polymerizing step mentioned above will be describedbelow. The HIPE polymerizing step dies not need to be particularlyrestricted but may be suitably selected from among the heretofore knownmethods of polymerizing an HIPE. Generally, the polymerization of anHIPE is effected by heating the HIPE by the stationary polymerizationtechnique under conditions incapable of disrupting the internalstructure of the HIPE. In this case, though the batch polymerizationwhich consists in subjecting one batch after another of the HIPE topolymerization and the continuous polymerization which consists incontinuously feeding the HIPE into a heating zone and meanwhile castingit are both effectively applicable to the HIPE, the continuouspolymerization is preferred over the batch polymerization as a method ofpolymerization for the sake of putting the effect of short-timepolymerization which is a characteristic feature of this invention toadvantage and exalting the productivity of the operation. Specifically,a method of continuous polymerization which comprises continuouslycasting an HIPE in the form of a sheet or a film onto a traveling beltand heating the cast HIPE till polymerization may be cited as a concreteexample of the continuous method under discussion. In this case, it isadvantageous to use the method of Japanese Patent Application No.11-314397 which comprises applying a specific oxygen content decreasingmeans to the outer surface part of an emulsion.

[0085] 2. HIPE Polymerizing Temperature T₂

[0086] Though the temperature T₂ during the HIPE polymerizing step ofthis invention generally is in the range of 40-110° C., this inventionrequires to control this temperature T₂ so that the temperature of theHIPE during this step may not produce a change exceeding 10° C. relativeto the temperature T₀ during the HIPE forming step and the temperatureT₁ during the HIPE shaping step. That is, this polymerizing temperatureT₂ is controlled to a level within 10° C. from the HIPE formingtemperature T₀C. and the HIPE shaping temperature T₁.

[0087] If the polymerizing temperature T₂ has a difference exceeding 10°C. from T₀ and T₁, the excess will be at a disadvantage in affecting theuniformity of emulsion during the polymerizing step, inducing adiscernible sign of partial degradation of the emulsion, giving rise tonumerous minute voids in the emulsion, largely degrading the absorptionproperties of the finished product, and unduly elongating the timerequired for the polymerizing step. Again in this case, the differenceof temperature is within 5° C. and preferably within 2° C.

[0088] For the purpose of controlling the HIPE polymerizing temperatureT₂ so that it may not produce a change exceeding 10° C. relative to theHIPE shaping temperature T₁, it is necessary that the HIPE in process ofconveyance from the shaping step to the polymerizing zone be insulatedand the polymerization vessel be heated and insulated fullysatisfactorily. The term “polymerizing step” as used in this inventionis defined as extending from the time the shaping of an HIPE iscompleted through the time the HIPE is deprived of the fluidity at leastby polymerization. It, for example, refers to the step which terminateswhen the rate of polymerization approximately reaches 30%, preferably50%. Till this termination, the control of the temperature contemplatedby this invention must be carried out very attentively.

[0089] When the conditions mentioned above are satisfied, the HIPEpolymerizing temperature T₂ preferably is rather higher than otherwise.It is approximately in the range of 60°-110° C. and preferably in therange of 80°-105° C., for example.

[0090] 3. HIPE Polymerizing Time

[0091] The method of this invention, when the polymerization initiatorand the polymerization temperature used therein are optimized, forms avery effective means to effect stable production of a porous polymer ofuniform nature and behavior in a very short period of time as in therange of several tens of seconds to 30 minutes. Specifically, in thefirst, second, and third aspects of this invention, the polymerizingtime is preferably within 30 minutes, more preferably within 10 minutes,and particularly preferably in the range of 1-10 minutes. If the polymercuring time exceeds 30 minutes and reaches 60 minutes or 120 minutes,for example, the excess will be possibly at a disadvantage economicallyand industrially in degrading the productivity of the operation. Ofcourse, this invention does not exclude such conditions as these.Incidentally, if this time falls short of one minute, the shortage willpossibly prevent the porous polymer from acquiring fully satisfactorystrength.

[0092] The term “polymerizing time” as used herein is intended to referto the total time which elapses since the HIPE enters the polymerizingzone till its departs from the polymerizing zone. The polymerizingtemperature T₂, however, does not need to be fixed throughout the“polymerizing time” as described above. Particularly while the HIPE ismanifesting fluidity during the initial stage of polymerization, namelywhen this temperature T₂during the “polymerizing step” of this inventionremains within the range of temperature contemplated by this invention,the temperature may be changed with the object of promoting thesubsequent polymerization within such a range as avoids impairing thequality of the finished product.

[0093] Further, this invention is preferred to restrict the polymerizingtime mentioned above within 30 minutes and control the quantity of thepolymerization initiator to be completely decomposed within thepolymerizing time in the range of 0.05-2.0 mol % of the quantity of thepolymerizing monomer component. By controlling the quantity within thisrange, it is made possible to manufacture a porous polymer excelling inthe solid state properties of foam in a short period of time within 30minutes with very high productivity. This quantity in any case denotesthat of the polymerization initiator which is completely decomposedwithin the polymerizing time. So long as this quantity is controlledwithin the range, the total quantity of the polymerization initiator tobe used does not need to be particularly restricted. If the quantity ofthe polymerization initiator which is completely decomposed within thepolymerizing time falls short of 0.05 mol %, the shortage will result inpreventing the polymerization from being completed fully satisfactorilywithin the short period of time within 30 minutes and rendering theporous cross-linked polymer deficient in solid state properties.Conversely, if the quantity of the polymerization initiator to becompletely decomposed within the polymerizing time exceeds 2.0 mol %,the excess will possibly render the produced porous cross-linked polymerdeficient in such mechanical properties as compressive strength owing toa decrease in molecular weight, for example. This fact calls for muchheed. The quantity of the polymerization initiator to be completelydecomposed within the polymerizing time of not more than 30 minutes iscommendably controlled in the range of 0.10-1.0 mol %, and preferably inthe range of 0.15-0.5 mol %. Incidentally, the quantity (mol %) of thepolymerization initiator to be completely decomposed within thepolymerizing time can be found by the calculation which is described inJapanese Patent Application No. 290141/1999.

[0094] 4. Polymerizing Apparatus

[0095] The polymerizing apparatus which can be used for this inventiondoes not need to be particularly restricted but may be properly selectedfrom among the heretofore known chemical devices and used eitherdirectly or with necessary modification on the condition of befittingthe particular method of polymerization to be adopted. For example, apolymerization vessel so shaped as to suit the purpose of use of theproduced polymer may be utilized for the batch polymerization and such acontinuous polymerizing device as a belt conveyor which is provided witha compressing roller may be utilized for the continuous polymerization.Such a polymerizing apparatus is supplemented with a heating means and acontrolling means befitting the particular method of polymerization inuse such as, for example, a heating means which can heat a givenemulsion to the polymerizing temperature and maintain it at thistemperature by dint of such an active thermal energy ray as microwave ornear infrared ray capable of utilizing radiant energy or such a thermalmedium as hot water or hot air, though not exclusively. The surface ofthe HIPE which has been placed in the polymerization vessel inpreparation for batch polymerization and the surface (both the upper andlower sides) of the HIPE which has been cast on such a drive conveyingdevice as a conveyor in preparation for continuous polymerization ispreferred to remain in a state not exposed to the ambient air(specifically the oxygen component of the air) between the time thepolymerization is started and the time it is completed. For thispurpose, it is commendable to seal the HIPE surface with a varyingsealing material by way of allaying the action of the oxygen in the air.The material of which the polymerizing apparatus is made does not needto be particularly restricted. As typical examples of the material,metals and alloys thereof such as aluminum, iron, and stainless steel,synthetic resins such as polyethylene, polypropylene, fluorocarbonresins, polyvinyl chloride, and unsaturated polyester resin, andfiber-reinforced resins (FRP) having such synthetic resins reinforcedwith fibers such as glass fibers or carbon fibers may be cited.

[0096] 5. After treatment of Porous Polymer Obtained by Polymerization

[0097] The porous polymer which is obtained by the polymerizing stepmentioned above may assume an arbitrary form based on the shape whichhas been imparted at the shaping step mentioned above. Specifically,since it generally assumes the same form as is imparted by the shapingduring the course of polymerization, it suffices to perform the shapingin a form fit for the purpose of use of the final product. Optionally,the HIPE may be polymerized in the form of a sheet having a thickness ofabout 50 mm and then after treated in an arbitrary form as by slicingthe sheet into sheets or films 5 mm in thickness. Also by the method ofcontinuous polymerization, an HIPE in the form of a sheet or a film maybe horizontally conveyed and meanwhile polymerized and then aftertreated in an arbitrary form. In this case, a method which consists iscontinuously polymerizing an HIPE in the form of a sheet or a film notmore than 50 mm in thickness and then sliding the sheet or the film intosheets each having a thickness of 5 mm may be employed, for example.

[0098] (d) Aftertreating (Reduction to Finished Product) Step afterFormation of Porous Polymer

[0099] 1. Dehydration

[0100] The porous polymer obtained as described above is generallydehydrated by compression, decompressive aspiration, or the combinationthereof. Generally the dehydration thus performed removes 50-98% of thewater used, with the remainder of the water adhering to the porouspolymer. The rate of this dehydration is properly set, depending as onthe purpose of use of the porous polymer. Generally, it suffices to setthis rate so that the porous polymer in a perfectly dried state may havea water content in the range of 0.5-10 g or in the range of 1-5 g per g.of the polymer.

[0101] 2. Compression

[0102] The porous polymer of this invention, depending on the kind ofitself, can be compressed to one of several parts of the originalthickness. The form such as of a compressed sheet has a small volume ascompared with the original porous polymer and permits a saving in thecost of transportation and storage. The porous polymer in the compressedform, on exposure to a large volume of water, is disposed to absorbwater and resume the original thickness. This absorption of water ischaracterized by the fact that the speed thereof is higher than thespeed at which the porous polymer in the original thickness absorbswater.

[0103] For the purpose of enabling the porous polymer to assume thecompressed form, it suffices to use a compressing means fit for the formof the porous polymer so as to exert uniform pressure on the entireporous polymer and compress it uniformly. Incidentally, the porouspolymer in the form of a sheet proves advantageous because it enablesthe pressure to be easily applied uniformly throughout the entire volumethereof, allows use of any of numerous existing compressing devices, andpermits such a device to be operated easily. After the porous polymer inthe form of a sheet has been dehydrated, it only needs to pass betweenrolls or belts opposed to each other across a prescribed interval. Sincethe sheet generally incurs a slight decrease in thickness in consequenceof the application of compression during the dehydrating step or theoperation of decompressive aspiration, the elaborate incorporation ofthe compressing step is not justified when the thickness of the sheetafter the dehydrating step falls within the prescribed range. In thecase of such a porous polymer in the form of other than a sheet as theporous polymer in a cylindrical form, for example, the impartation of acompressed state to the cylindrical porous polymer may be accomplishedby preparing a larger deformable cylinder made of a metal and a smallerconcentrically uniformly inflatable cylinder made of a rubber tube,disposing the larger and smaller cylinders respectively outside andinside the cylindrical wall of the porous polymer, and compressing theintervening cylindrical wall of the porous polymer by introducing airinto the tube of the inner cylinder. Thus, the necessary compression maybe attained by using a proper device which fits the form of the porouspolymer. Otherwise, the compression may be fulfilled by wrapping theporous polymer in the cylindrical form around a rotary shaft conformingto the inside diameter of the cylindrical porous polymer, setting a rollfast against the outer side of the cylindrical wall of the porouspolymer, and rotating the rotary shaft and the roll as pressed againstthe opposite surfaces of the cylindrical wall of the porous polymer.

[0104] The temperature at which the porous polymer is compressed at thepreceding dehydrating and compressing steps is preferred to be higherthan the glass transition point of the porous polymer. If thistemperature is lower than the glass transition point, the shortage willpossibly result in disrupting the porous structure of the polymer oraltering the pore diameter of the polymer.

[0105] From the viewpoint of saving the space necessary fortransportation and storage and ensuring the ease of handling, it iseffective to compress the porous polymer to not more than ½, preferablyto not more than ¼, of the original thickness thereof.

[0106] 3. Washing

[0107] For the purpose of improving the porous polymer in the surfacecondition, the porous polymer may be washed with purified water, anaqueous solution containing an arbitrary additive, or solvent.

[0108] 4. Drying

[0109] The porous polymer which has been obtained by the precedingsteps, when necessary, may be dried by heating with hot air, infraredrays, or microwaves or may be furnished with an adjusted water contentby humidification.

[0110] 5. Cutting

[0111] The porous polymer which has been obtained by the precedingsteps, when necessary, may be cut in a form and a size as required byway of working into a finished product fit for the purpose of use.

[0112] 6. Impregnation

[0113] The porous polymer may be impregnated with such additives as adetergent, an aromatizer, a deodorant, or an antibacterial agent so asto be endowed with a relevant functionality.

[0114] The second and third aspects of this invention, as alreadypointed out, have such a principal necessary condition for constructionas controlling the temperature of an HIPE at each of the steps lest itshould produce a change exceeding 10° C. and continuously subjecting theHIPE to (i) a forming, (ii) a shaping, and (iii) a polymerizing step.Generally, the condition equals a method for continuously producing aporous polymer by continuously forming an HIPE, shaping the HIPE on adrive conveying device, and polymerizing the shaped porous polymer.According to the second and third aspects of this invention, since theoperation is continuously carried out consistently, the control of thetemperature during each of the component steps of the invention iseasily implemented and the porous polymer foam having uniform excellentsolid state properties can be obtained in such a very short period oftime as has never been predicted. Further, since the series of componentsteps of the process of production can be continuously carried out, theproduction proceeds with a very high operational efficiency and proveshighly efficient economically and industrially.

[0115] [II] Now, the fourth, fifth, and sixth aspects of this inventionwill be described in detail below.

[0116] The fourth aspect of this invention is directed toward a methodfor the production of a porous polymer by the polymerization of awater-in-oil type high internal phase emulsion obtained from an oilphase containing a polymerizing monomer component and a surfactant and awater phase containing water, which method is characterized bycomprising

[0117] (a) an emulsifying step for forming a water-in-oil type highinternal phase emulsion,

[0118] (b) a forming step for forming the emulsion in the form of asheet or a film, and

[0119] (c) a polymerizing step for polymerizing the emulsion and havingthe component steps of the process mentioned above to proceed invariablyat a temperature of not lower than 80° C. and not higher than 110° C.

[0120] The fifth aspect of this invention is directed toward a methodfor the production of a porous polymer by the polymerization of awater-in-oil type high internal phase emulsion obtained from an oilphase containing a polymerizing monomer component and a surfactant and awater phase containing water, which method is characterized bycomprising

[0121] (a) a continuous emulsifying step for continuously forming awater-in-oil type high internal phase emulsion,

[0122] (b) a continuous forming step for continuously forming theemulsion in the form of a sheet or a film, and

[0123] (c) a continuous polymerizing step for continuously polymerizingthe emulsion

[0124] and having the component steps of the process mentioned above toproceed invariably at a temperature of not lower than 80° C. and nothigher than 110° C.

[0125] The sixth aspect of this invention is directed toward a methodfor the production of a porous polymer by the polymerization of awater-in-oil type high internal phase emulsion obtained from an oilphase containing a polymerizing monomer component and a surfactant and awater phase containing water, which method is characterized bycomprising

[0126] (a) a continuous emulsifying step for continuously forming awater-in-oil type high internal phase emulsion,

[0127] (b) a continuous forming step for continuously forming theemulsion in a thickness of not more than 50 mm, and

[0128] (c) a continuous polymerizing step for continuously polymerizingthe emulsion

[0129] and having the component steps of the process mentioned above toproceed invariably at a temperature of not lower than 80° C. and nothigher than 110° C.

[0130] For the fourth, fifth, and sixth aspects of this invention, thefact that (a) the forming step, (b) the shaping step, and (c) thepolymerizing step respectively of an HIPE are invariably carried out attemperatures exceeding 80° C. and not exceeding 110° C. forms aprincipal necessary condition for construction. By fulfilling thisnecessary condition, it is made possible to eliminate the loss of thefine uniformity of the foam caused by the heat shock which is observedwhen the HIPE is formed at a temperature lower than 80° C. and cured ata temperature higher than 80° C. or when the HIPE is formed at atemperature higher than 80° C. and this temperature nevertheless issuffered to fall during the shaping step and is subsequently elevated toa level higher than 80° C., at which the HIPE is polymerized. The porouspolymer which excels in performance is obtained in a very short periodof time with high productivity because the polymerization is carried outat such a high temperature as not lower than 80° C. and not higher than110° C. In this case, the forming temperature T₀, the shapingtemperature T₁, and the polymerizing temperature T₂ respectively of theHIPE are generally not lower than 80° C. and not higher than 110° C.They are preferably in the range of 85°-105° C. and more preferably inthe range of 90°-100° C. Again in this case, it is commendable to keepthe change of temperature of the water-in-oil type high internal phaseemulsion during each of the steps ranging from the formation through thepolymerization of the water-in-oil type high internal phase emulsionwithin 10° C. and preferably within 5° C.

[0131] For the fifth and sixth aspects of this invention, too, the factthat the HIPE is continuously (i) formed, (ii) shaped, and (iii)polymerized while the temperature of the HIPE is controlled to a levelof not higher than 80° C. and not lower than 110° C. forms a principalnecessary condition. In this case again, since the operation iscontinuously carried out consistently, the control of the temperature ofthe HIPE at a level of not higher than 80° C. and not lower than 110° C.is easily implemented and the porous polymer form endowed with uniformand excellent solid state properties can be obtained in such a veryshort period of time as has never been predicted. Further, since theseries of component steps of the process of production can becontinuously carried out, the production proceeds with a very highoperational efficiency and proves highly efficient economically andindustrially.

[0132] In the fourth, fifth, and sixth aspects of the invention, theother necessary conditions for construction are basically the same asthose described above with respect to the first through third aspects ofthe invention.

[0133] [III] The seventh method of production contemplated by thisinvention will be described in detail below.

[0134] The seventh aspect of this invention is directed toward a methodfor the production of a porous polymer by the polymerization of awater-in-oil type high internal phase emulsion obtained from an oilphase containing a polymerizing monomer component and a surfactant and awater phase containing water, which method is characterized bycomprising

[0135] (a) a continuous emulsifying step for continuously forming awater-in-oil type high internal phase emulsion,

[0136] (b) a continuous forming step for continuously forming theemulsion in a necessary shape, and

[0137] (c) a continuous polymerizing step for continuously polymerizingthe emulsion

[0138] and having the component steps of the process mentioned above toproceed invariably at a temperature of not lower than 80° C. and havinga polymerization initiator incorporated in the emulsion after the startof (a) the continuous emulsifying step and before the completion of (b)the continuous forming step.

[0139] The seventh aspect of this invention purports to have (a) theforming step, (b) the shaping step, and (c) the polymerizing steprespectively of an HIPE carried out at temperatures invariably exceeding80° C. and continuously and effect the addition of a polymerizationinitiator between (a) the time the continuous emulsifying step mentionedabove is started and the time (b) the continuous forming step mentionedabove is completed.

[0140] As typical examples of the way of adding the polymerizationinitiator to the HIPE, (i) a method which comprises adding thepolymerization initiator to the water phase and/or the oil phase inadvance of the formation of the HIPE and mixing them, (ii) a methodwhich consists in adding the polymerization initiator at the same timeas the HIPE is formed and mixing them, and (iii) a method which consistsin adding the polymerization initiator after the HIPE has been formedmay be cited. Where (a) the forming step, (b) the shaping step, and (c)the polymerizing step are carried out continuously at temperaturesinvariably exceeding 80° C., however, the polymerizing monomer componentin process of emulsification possibly begins to polymerize, forms apolymer, and prevents the continuous production from being performed ina stable manner, depending on the kind of polymerizing initiator and themethod of addition particularly in the case of (a) the method mentionedabove. To avoid this accident, the seventh aspect of this invention addsthe polymerization initiator between the time (a) the continuousemulsifying step mentioned above is started and the time the continuousshaping step (b) mentioned above is completed.

[0141] In consequence of this timing of the addition, the HIPE at anelevated temperature can be smoothly formed, shaped, and polymerized andthe foam endowed with excellent absorption properties can be obtainedwith exceptionally high productivity. As a way of adding and mixing thepolymerization initiator, a method of continuously adding thepolymerization initiator to the HIPE via an inlet port disposed at anarbitrary position in the path extending from the site for the formationof the HIPE through the site for the completion of the HIPE shaping stepand further continuously mixing them by the use of such a line mixer asa static mixer is advantageously used.

[0142] Incidentally, the kind of a polymerization initiator and thequantity thereof to be used herein are the same as those described inthe paragraph (4) dealing with a polymerization initiator in thesection 1. titled “Raw materials used for HIPE”. Further, in the redoxinitiator system, too, the polymerizing monomer component in process ofemulsification does not easily begin to polymerize and the continuousproduction is carried out in a stable manner so long as the method ofaddition contemplated by the seventh aspect of this invention is appliedto either an oxidizing agent or a reducing agent.

[0143] In the seventh aspect of this invention, the other necessaryconditions for construction are basically the same as those describedabove with respect to the first through sixth aspects of the invention.

[0144] Now, this invention will be described more specifically belowwith reference to working examples. In these working examples, theperformance of a given porous polymer was determined and evaluated asfollows.

[0145] <Degree of Water Release and Surface Condition of Porous Polymer>

[0146] The fine uniformity of the surface of a produced porous polymerwas determined by visually observing a spot of the surface magnified to50 times the original size with the aid of an SEM and evaluating theresult of the observation.

[0147] <Compressive Strength>

[0148] The monoaxial (direction of thickness) compressive strength of agiven sample was determined at 24° C. by the use of a testing device(made by Instron Corp. and sold under registered trademark designationof “Instron 1186-RE5500”) and reported as reduced to the internationalunit system (kPa).

[0149] <Preparation of Artificial Urine>

[0150] An artificial urine was prepared by dissolving 10 mass parts ofKCl, 10 mass parts of Na₂SO₄, 4.25 mass parts of NH₄H₂PO₄, 0.75 masspart of (NH₄)₂HPO₄, 1.25 mass parts of CaCl₂.2H₂O, and 2.5 mass parts ofMgCl₂.6H₂O in 4971.25 mass parts of deionized water.

[0151] <Height of Suction>

[0152] A strip 1 cm in width and 80 cm in length was cut from a givenporous polymer sample and suspended vertically from one end thereof. Thelower leading end of this strip was immersed to a length of about 4 cmin a large quantity of the artificial urine prepared as described andleft standing in this state for three days, with the pool of the urinereplenished with new supply from time to time to maintain the levelconstant. At the end of the 3 days' standing, the foam which hadabsorbed the urine was pulled up till the height of the lowermost partnot immersed in the artificial urine thereof decreased to 0 cm. Theremoved foam was cut into unit heights of 2 cm, which were each weighed(W₁).

[0153] The unit heights were dried and then each weighed (W₀). Thecapacity for absorption of each of the unit heights was found bycalculation (W₁/W₀).

[0154] The height of the part of the foam equivalent to the capacity ofabsorption of 90%, based on the capacity of absorption of 100% ofthepart of theheight of 0 cm not immersed in the artificial urine, wasdetermined and reported as the height of absorption (cm).

EXAMPLE 1

[0155] An oil phase mixture solution (hereinafter referred to as “oilphase”) was prepared by adding together a monomer component composed of5.1 mass parts (hereinafter referred to briefly as “parts”) of2-ethylhexyl acrylate, 3.1 parts of 42% divinyl benzene (p-ethyl-vinylbenzene as the other moiety), and 1.1 parts of 1,6-hexanediol diacrylateand 0.6 part of glycerol monooleate and 0.1 part of ditallow dimethylammonium methyl sulfate as surfactants and uniformly dissolving them.Separately, an aqueous water phase solution (hereinafter referred to as“water phase”) was prepared by dissolving 18 parts of calcium chloridein 425 parts of deionized water and heated to 85° C. A water-in-oil typehigh internal phase emulsion (HIPE) was continuously formed bycontinuously feeding the oil phase and the water phase at the ratioindicated above into a stirring-mixing device. The ratio of the waterphase and the oil phase was 44.3/1 and the forming temperature T₀ of theHIPE was 85° C.

[0156] The HIPE consequently formed was continuously extracted from thestirring-mixing device, heated preparatorily to 85° C., and supplied toa static mixer provided in the periphery thereof with a heating and aninsulating member. A liquid obtained by dissolving 0.5 part of sodiumpersulfate as a water-soluble polymerization initiator in 6 parts ofdeionized water was fed to the static mixer via an inlet port so as tomix the HIPE with the polymerization inhibitor continuously.Consequently, the ratio of the water phase and the oil phase eventuallychanged to 45/1.

[0157] The HIPE was conveyed through an insulated and heated flexibletube, cast into a square polymerization vessel of stainless steelmeasuring 1100 mm in length, 100 mm in width, and 5 mm in wall thicknessand kept preparatorily at 85° C. by insulation, and shaped therein. Theshaping temperature T₁ of the HIPE was 81° C. The polymerization vesselwas stoppered on the upper side and then immersed in a water bathadapted to fix the polymerizing temperature T₂ of the HIPE at 85° C. Thevessel was pulled up from the water bath 15 minutes after the start ofheating to obtain a cured wet porous polymer. The quantity of thepolymerization inhibitor to be completely decomposed over 15 minutes ofthe polymerizing time was found to be 0.314 mol %. By dehydrating andcompressing this porous polymer, a porous polymer (1) having a watercontent of about 20% based on the weight of the porous polymer in adried state was obtained. This porous polymer (1) was visually examinedfor surface condition with an SEM and tested for compressive strengthand height of absorption. The results are shown in Table 1 below.

EXAMPLE 2

[0158] The same polymerization initiator-containing HIPE as was obtainedin Example 1 (the forming temperature T₀=85° C.) was conveyed through aninsulated and heated flexible tube, cast onto a traveling belt heated to85° C., installed horizontally, and driven at a fixed speed andcontinuously shaped in the form of a sheet about 50 cm in width andabout 5 mm in thickness. The shaping temperature T₁ of the HIPE was 82°C. This HIPE was passed through a polymerizing zone having apolymerizing temperature T₂ controlled at 85° C. so as to be polymerizedcontinuously and made to form a cured wet porous polymer. The quantityof the polymerization inhibitor to be completely decomposed in 15minutes of the polymerizing time was found to be 0.314 mol %. Bydehydrating and compressing this porous polymer, a porous polymer (2)having a water content of about 20% based on the quantity of the porouspolymer in a dried state was obtained. This porous polymer (2) wasvisually examined for surface condition with an SEM and tested forcompressive strength and height of absorption. The results are shown inTable 1 below.

EXAMPLE 3

[0159] An oil phase mixture solution (hereinafter referred to as “oilphase”) was prepared by adding together a monomer component composed of4.9 parts of 2-ethylhexyl acrylate, 3.2 parts of 42% divinyl benzene(p-ethyl-vinyl benzene as the other moiety), and 1.2 parts of1,6-hexanediol diacrylate and 0.6 part of glycerol monooleate and 0.1part of ditallow dimethyl ammonium methyl sulfate as surfactants anduniformly dissolving them. Separately, an aqueous water phase solution(hereinafter referred to as “water phase”) was prepared by dissolving 18parts of calcium chloride in 425 parts of deionized water and heated to95° C. A water-in-oil type high internal phase emulsion (HIPE) wascontinuously formed by continuously feeding the oil phase and the waterphase at the ratio indicated above into a stirring-mixing device. Theratio of the water phase and the oil phase was 44.3/1 and the formingtemperature T₀ of the HIPE was 95° C.

[0160] The HIPE consequently formed was continuously extracted from thestirring-mixing device, heated preparatorily to 95° C., and supplied toa static mixer provided in the periphery thereof with a heating and aninsulating member. A liquid obtained by dissolving 0.5 part of sodiumpersulfate as a water-soluble polymerization initiator in 6 parts ofdeionized water was fed to the static mixer via an inlet port so as tomix the HIPE with the polymerization inhibitor continuously.Consequently, the ratio of the water phase and the oil phase eventuallychanged to 45/1.

[0161] The HIPE was conveyed through an insulated and heated flexibletube, cast into a square polymerization vessel of stainless steelmeasuring 1100 mm in length, 100 mm in width, and 5 mm in wall thicknessand kept preparatorily at 85° C. by insulation, and shaped therein. Theshaping temperature T₁ of the HIPE was 92° C. The polymerization vesselwas stoppered on the upper side and then immersed in a water bathadapted to fix the polymerizing temperature T₂ of the HIPE at 95° C. Thevessel was pulled up from the water bath 5 minutes after the start ofheating to obtain a cured wet porous polymer. The quantity of thepolymerization inhibitor to be completely decomposed over 5 minutes ofthe polymerizing time was found to be 0.295 mol %. By dehydrating andcompressing this porous polymer, a porous polymer (3) having a watercontent of about 20% based on the weight of the porous polymer in adried state was obtained. This porous polymer (3) was visually examinedfor surface condition with an SEM and tested for compressive strengthand height of absorption. The results are shown in Table 1 below.

EXAMPLE 4

[0162] The same polymerization initiator-containing HIPE as was obtainedin Example 3 (the forming temperature T₀=95° C.) was conveyed through aninsulated and heated flexible tube, cast onto a traveling belt heated to95° C., installed horizontally, and driven at a fixed speed andcontinuously shaped in the form of a sheet about 50 cm in width andabout 5 mm in thickness. The shaping temperature T₁ of the HIPE was 92°C. This HIPE was passed through a polymerizing zone having apolymerizing temperature T₂ controlled at 96° C. so as to be polymerizedcontinuously and made to form a cured wet porous polymer. The quantityof the polymerization inhibitor to be completely decomposed in 15minutes of the polymerizing time was found to be 0.295 mol %. Bydehydrating and compressing this porous polymer, a porous polymer (4)having a water content of about 20% based on the quantity of the porouspolymer in a dried state was obtained. This porous polymer (4) wasvisually examined for surface condition with an SEM and tested forcompressive strength and height of absorption. The results are shown inTable 1 below.

EXAMPLE 5

[0163] An HIPE was formed by following the procedure of Example 3 whileusing an aqueous water phase solution heated to 85° C. (the formingtemperature T₀=85° C). The polymerization initiator-containing HIPE thusobtained was conveyed through an insulated and heated flexible tube,cast onto a traveling belt heated to 95° C., installed horizontally, anddriven at a fixed speed and continuously shaped in the form of a sheetabout 50 cm in width and about 5 mm in thickness. The shapingtemperature T₁ of the HIPE was 82° C. This HIPE was passed through apolymerizing zone having a polymerizing temperature T₂ controlled at 96°C. so as to be polymerized continuously and made to form a cured wetporous polymer. The quantity of the polymerization inhibitor to becompletely decomposed in 7 minutes of the polymerizing time was found tobe 0.336 mol %. By dehydrating and compressing this porous polymer, aporous polymer (5) having a water content of about 20% based on thequantity of the porous polymer in a dried state was obtained. Thisporous polymer (5) was visually examined for surface condition with anSEM and tested for compressive strength and height of absorption. Theresults are shown in Table 1 below.

EXAMPLE 6

[0164] An oil phase mixture solution (hereinafter referred to as “oilphase”) was prepared by adding together a monomer component composed of4.9 parts of 2-ethylhexyl acrylate, 3.2 parts of 42% divinyl benzene(p-ethyl-vinyl benzene as the other moiety), and 1.2 parts of1,6-hexanediol diacrylate and 0.6 part of glycerol monooleate and 0.1part of ditallow dimethyl ammonium methyl sulfate as surfactants anduniformly dissolving them. Separately, an aqueous water phase solution(hereinafter referred to as “water phase”) was prepared by dissolving 18parts of calcium chloride in 425 parts of deionized water and heated to98° C. A water-in-oil type high internal phase emulsion (HIPE) wascontinuously formed by continuously feeding the oil phase and the waterphase at the ratio indicated above into a stirring-mixing device. Theratio of the water phase and the oil phase was 44.3/1 and the formingtemperature T₀ of the HIPE was 98° C.

[0165] The HIPE consequently formed was continuously extracted from thestirring-mixing device, heated preparatorily to 96° C., and supplied toa static mixer provided in the periphery thereof with a heating and aninsulating member. A liquid obtained by dissolving 0.5 part of sodiumpersulfate as a water-soluble polymerization initiator in 5 parts ofdeionized water was fed to the static mixer via an inlet port so as tomix the HIPE with the polymerization inhibitor continuously.Consequently, the ratio of the water phase and the oil phase eventuallychanged to 45/1.

[0166] The HIPE was conveyed through an insulated and heated flexibletube, cast onto a belt heated to 96° C., installed horizontally, anddriven at a fixed speed, and continuously formed into a sheet about 50cm in width and about 5 mm in thickness. The shaping temperature T₁ ofthe HIPE was 95° C. This HIPE was continuously polymerized by beingpassed through a polymerizing zone having a polymerizing temperature T₂controlled to 96° C. over a period of about 5 minutes so as to obtain acured wet porous polymer. The quantity of the polymerization inhibitorto be completely decomposed over 5 minutes of the polymerizing time wasfound to be 0.323 mol %. By dehydrating and compressing this porouspolymer, a porous polymer (6) having a water content of about 20% basedon the weight of the porous polymer in a dried state was obtained. Thisporous polymer (6) was visually examined for surface condition with anSEM and tested for compressive strength and height of absorption. Theresults are shown in Table 1 below.

EXAMPLE 7

[0167] An oil phase mixture solution (hereinafter referred to as “oilphase”) was prepared by adding together a monomer component composed of4.9 parts of 2-ethylhexyl acrylate, 3.2 parts of 42% divinyl benzene(p-ethyl-vinyl benzene as the other moiety), and 1.2 parts of1,6-hexanediol diacrylate and 0.6 part of glycerol monooleate and 0.1part of ditallow dimethyl ammonium methyl sulfate as surfactants anduniformly dissolving them. Separately, an aqueous water phase solution(hereinafter referred to as “water phase”) was prepared by dissolving 18parts of calcium chloride in 425 parts of deionized water and heated to98° C. A water-in-oil type high internal phase emulsion (HIPE) wascontinuously formed by continuously feeding the oil phase and the waterphase at the ratio indicated above into a stirring-mixing device. Theratio of the water phase and the oil phase was 44.3/1 and the formingtemperature T₀ of the HIPE was 98° C.

[0168] The HIPE consequently formed was continuously extracted from thestirring-mixing device, heated preparatorily to 85° C., and supplied toa static mixer provided in the periphery thereof with a heating and aninsulating member. A liquid obtained by dissolving 0.8 part of sodiumpersulfate as a water-soluble polymerization initiator in 7 parts ofdeionized water was fed to the static mixer via an inlet port so as tomix the HIPE with the polymerization inhibitor continuously.Consequently, the ratio of the water phase and the oil phase eventuallychanged to 45/1.

[0169] The HIPE was conveyed through an insulated and heated flexibletube, cast onto a belt heated to 96° C., installed horizontally, anddriven at a fixed speed, and continuously formed into a sheet about 50cm in width and about 5 mm in thickness. The shaping temperature T₁ ofthe HIPE was 95° C. This HIPE was continuously polymerized by beingpassed through a polymerizing zone having a polymerizing temperature T₂controlled to 96° C. over a period of about 4.5 minutes so as to obtaina cured wet porous polymer. The quantity of the polymerization inhibitorto be completely decomposed over 4.5 minutes of the polymerizing timewas found to be 0.492 mol %. By dehydrating and compressing this porouspolymer, a porous polymer (7) having a water content of about 20% basedon the weight of the porous polymer in a dried state was obtained. Thisporous polymer (7) was visually examined for surface condition with anSEM and tested for compressive strength and height of absorption. Theresults are shown in Table 1 below.

EXAMPLE 8

[0170] The same polymerization initiator-containing HIPE as was obtainedin Example 7 (the forming temperature T₀=98° C.) was conveyed through aninsulated and heated flexible tube, cast onto a traveling belt heated to96° C., installed horizontally, and driven at a fixed speed andcontinuously shaped in the form of a sheet about 50 cm in width andabout 5 mm in thickness. The shaping temperature T₁ of the HIPE was 95°C. This HIPE was passed through a polymerizing zone having apolymerizing temperature T₂ controlled at 96° C. over a period of about3.5 minutes so as to be polymerized continuously and made to form acured wet porous polymer. The quantity of the polymerization inhibitorto be completely decomposed in 3.5 minutes of the polymerizing time wasfound to be 0.380 mol %. By dehydrating and compressing this porouspolymer, a porous polymer (8) having a water content of about 20% basedon the quantity of the porous polymer in a dried state was obtained.This porous polymer (8) was visually examined for surface condition withan SEM and tested for compressive strength and height of absorption. Theresults are shown in Table 1 below.

EXAMPLE 9

[0171] An oil phase mixture solution (hereinafter referred to as “oilphase”) was prepared by adding together a monomer component composed of4.9 parts of 2-ethylhexyl acrylate, 3.2 parts of 42% divinyl benzene(p-ethyl-vinyl benzene as the other moiety), and 1.2 parts of1,6-hexanediol diacrylate and 0.6 part of glycerol monooleate and 0.1part of ditallow dimethyl ammonium methyl sulfate as surfactants anduniformly dissolving them. Separately, an aqueous water phase solution(hereinafter referred to as “water phase”) was prepared by dissolving 18parts of calcium chloride in 425 parts of deionized water and heated to98° C. A water-in-oil type high internal phase emulsion (HIPE) wascontinuously formed by continuously feeding the oil phase and the waterphase at the ratio indicated above into a stirring-mixing device. Theratio of the water phase and the oil phase was 44.3/1 and the formingtemperature T₀ of the HIPE was 98° C.

[0172] The HIPE consequently formed was continuously extracted from thestirring-mixing device, heated preparatorily to 96° C., and supplied toa static mixer provided in the periphery thereof with a heating and aninsulating member. A liquid obtained by dissolving 1.7 parts of sodiumpersulfate as a water-soluble polymerization initiator in 3.8 parts ofdeionized water was fed to the static mixer via an inlet port so as tomix the HIPE with the polymerization inhibitor continuously.Consequently, the ratio of the water phase and the oil phase eventuallychanged to 45/1.

[0173] The HIPE was conveyed through an insulated and heated flexibletube, cast onto a belt heated to 96° C., installed horizontally, anddriven at a fixed speed, and continuously formed into a sheet about 50cm in width and about 5 mm in thickness. The shaping temperature T₁ ofthe HIPE was 95° C. This HIPE was continuously polymerized by beingpassed through a polymerizing zone having a polymerizing temperature T₂controlled to 96° C. over a period of about 2.5 minutes so as to obtaina cured wet porous polymer. The quantity of the polymerization inhibitorto be completely decomposed over about 2.5 minutes of the polymerizingtime was found to be 0.545 mol %. By dehydrating and compressing thisporous polymer, a porous polymer (9) having a water content of about 20%based on the weight of the porous polymer in a dried state was obtained.This porous polymer (9) was visually examined for surface condition withan SEM and tested for compressive strength and height of absorption. Theresults are shown in Table 1 below

EXAMPLE 10

[0174] The same polymerization initiator-containing HIPE as was obtainedin Example 9 (the forming temperature T₀=98° C.) was conveyed through aninsulated and heated flexible tube, cast onto a traveling belt heated to85° C., installed horizontally, and driven at a fixed speed andcontinuously shaped in the form of a sheet about 50 cm in width andabout 5 mm in thickness. The shaping temperature T₁ of the HIPE was 96°C. This HIPE was passed through a polymerizing zone having apolymerizing temperature T₂ controlled at 96° C. so as to be polymerizedcontinuously and made to form a cured wet porous polymer. The quantityof the polymerization inhibitor to be completely decomposed in 3.5minutes of the polymerizing time was found to be 0.383 mol %. Bydehydrating and compressing this porous polymer, a porous polymer (10)having a water content of about 20% based on the quantity of the porouspolymer in a dried state was obtained. This porous polymer wascontinuously sliced perpendicularly to the direction of thickness with aband knife into two vertically separated sheets each measuring about 50cm in width and about 1 mm in thickness. The separated sheets were thendried further to obtain porous polymers (upper sheet 10-A and lowersheet 10-B) having a water content of about 20% based on the quantity ofthe porous polymer in a dried state. The porous polymer (10-A) andporous polymer (10-B) were visually examined for surface condition withan SEM and tested for compressive strength and height of absorption. Theresults are shown in Table 1 below.

[0175] Control 1

[0176] An oil phase mixture solution (hereinafter referred to as “oilphase”) was prepared by adding together a monomer component composed of5.1 mass parts (hereinafter referred to briefly as “parts”) of2-ethylhexyl acrylate, 3.1 parts of 42% divinyl benzene (p-ethyl-vinylbenzene as the other moiety), and 1.1 parts of 1,6-hexanediol diacrylateand 0.6 part of glycerol monooleate and 0.1 part of ditallow dimethylammonium methyl sulfate as surfactants and uniformly dissolving them.Separately, an aqueous water phase solution (hereinafter referred to as“water phase”) was prepared by dissolving 18 parts of calcium chloridein 425 parts of deionized water and heated to 65° C. A water-in-oil typehigh internal phase emulsion (HIPE) was continuously formed bycontinuously feeding the oil phase and the water phase at the ratioindicated above into a stirring-mixing device. The ratio of the waterphase and the oil phase was 44.3/1 and the forming temperature T₀ of theHIPE was 65° C.

[0177] The HIPE consequently formed was continuously extracted from thestirring-mixing device and supplied to a static mixer. A liquid obtainedby dissolving 0.5 part of sodium persulfate as a water-solublepolymerization initiator in 6 parts of deionized water was fed to thestatic mixer via an inlet port so as to mix the HIPE with thepolymerization inhibitor continuously. Consequently, the ratio of thewater phase and the oil phase eventually changed to 45/1.

[0178] The HIPE was conveyed through a flexible tube, cast into a squarepolymerization vessel of stainless steel measuring 1100 mm in length,100 mm in width, and 5 mm in wall thickness, and shaped therein. Theshaping temperature T₁ of the HIPE was 57° C. The polymerization vesselwas stoppered on the upper side and then immersed in a water bathadapted to fix the polymerizing temperature T₂ of the HIPE at 85° C. Thevessel was pulled up from the water bath 15 minutes after the start ofheating to obtain a cured wet porous polymer. The quantity of thepolymerization inhibitor to be completely decomposed over 15 minutes ofthe polymerizing time was found to be 0.255 mol %. By dehydrating andcompressing this porous polymer, a porous polymer (1) for control havinga water content of about 20% based on the weight of the porous polymerin a dried state was obtained. This porous polymer (1) for control wasvisually examined for surface condition with an SEM and tested forcompressive strength and height of absorption. The results are shown inTable 1 below.

[0179] Control 2

[0180] The same polymerization initiator-containing HIPE as was obtainedin Control 1 (the forming temperature T₀=65° C.) was conveyed through aflexible tube, cast onto a belt installed horizontally and driven at afixed speed, and continuously shaped thereon in the form of a sheetabout 50 cm in width and about 5 mm in thickness. The shapingtemperature T₁ of the HIPE was 55° C. This HIPE was continuouslypolymerized by being passed over a period of about 15 minutes through apolymerizing zone having a polymerizing temperature T₂ controlled at 85°C. so as to form a cured wet porous polymer. The quantity of thepolymerization inhibitor to be completely decomposed in 15 minutes ofthe polymerizing time was found to be 0.255 mol %. By dehydrating andcompressing this porous polymer, a porous polymer (2) for control havinga water content of about 20% based on the quantity of the porous polymerin a dried state was obtained. This porous polymer (2) for control wasvisually examined for surface condition with an SEM and tested forcompressive strength and height of absorption. The results are shown inTable 1 below.

[0181] Control 3

[0182] An HIPE was formed by following the procedure of Control 1 whileusing an aqueous water phase solution heated to 55° C. (the formingtemperature T₀=85° C.). This polymerization initiator-containing HIPEwas conveyed through a flexible tube, cast onto a belt installedhorizontally and driven at a fixed speed, and continuously shaped in theform of a sheet about 50 cm in width and about 5 mm in thickness. Theshaping temperature T₁ of the HIPE was 50° C. This HIPE was passed overa period of about 7 minutes through a polymerizing zone having apolymerizing temperature T₂ controlled at 95° C. so as to be polymerizedcontinuously and made to form a cured wet porous polymer. The quantityof the polymerization inhibitor to be completely decomposed in 7 minutesof the polymerizing time was found to be 0.184 mol %. By dehydrating andcompressing this porous polymer, a porous polymer (3) for control havinga water content of about 20% based on the quantity of the porous polymerin a dried state was obtained. This porous polymer (3) for control wasvisually examined for surface condition with an SEM and tested forcompressive strength and height of absorption. The results are shown inTable 1 below.

[0183] Control 4

[0184] An HIPE was formed by following the procedure of Example 3 whileusing an aqueous water phase solution heated to 85° C. (the formingtemperature T₀=85° C.). This polymerization initiator-containing HIPEwas conveyed through a flexible tube, cast onto a belt installedhorizontally and driven at a fixed speed, and continuously shaped in theform of a sheet about 50 cm in width and about 5 mm in thickness. Theshaping temperature T₁ of the HIPE was 77° C. This HIPE was passed overa period of about 7 minutes through a polymerizing zone having apolymerizing temperature T₂ controlled at 95° C. so as to be polymerizedcontinuously and made to form a cured wet porous polymer. The quantityof the polymerization inhibitor to be completely decomposed in 7 minutesof the polymerizing time was found to be 0.336 mol %. By dehydrating andcompressing this porous polymer, a porous polymer (4) for control havinga water content of about 20% based on the quantity of the porous polymerin a dried state was obtained. This porous polymer (2) was visuallyexamined for surface condition with an SEM and tested for compressivestrength and height of absorption. The results are shown in Table 1below. TABLE 1 HIPE forming HIPE shaping HIPE Visual temperature,temperature, polymerizing Polymerizing examination of Compressive Heightof T₀ T₁ temperature, time surface condition strength absorption (° C.)(° C.) T₂ (° C.) (min) with SEN (kPa) (cm) Example 1 porous polymer 8581 85 15 homogeneous 9.8 58 (1) Example 2 porous polymer 85 82 85 15homogeneous 10.2 60 (2) Example 3 porous polymer 95 92 95 5 homogeneous9.7 56 (3) Example 4 porous polymer 95 92 96 5 homogeneous 9.8 57 (4)Example 5 porous polymer 85 82 96 7 homogeneous 9.9 60 (5) Example 6porous polymer 98 95 96 5 homogeneous 9.9 62 (6) Example 7 porouspolymer 98 95 96 4.5 homogeneous 10.1 62 (7) Example 8 porous polymer 9895 96 3.5 homogeneous 9.9 60 (8) Example 9 porous polymer 98 95 96 2.5homogeneous 9.7 60 (9) Example porous polymer 98 96 96 3.5 homogeneous9.8 60 10 (10-A) porous polymer 98 96 96 3.5 homogeneous 9.7 59 (10-B)Control 1 porous polymer 65 57 85 15 many voids 9.1 44 (1) for controlControl 2 porous polymer 65 55 85 15 many voids 9.2 48 (2) for controlControl 3 porous polymer 55 50 95 7 many voids 8.7 41 (3) for controlControl 4 porous polymer 85 77 95 7 there is voids 9.0 53 (4) forcontrol

[0185] Industrial Applicability

[0186] The electro conductive low thermal expansion ceramic originatingin this invention, as described in detail above, can give rise tomaterials for precision machine parts which enjoy such light weight andhigh dimensional stability as make the parts fit for use in anenvironment demanding a high degree of cleanliness.

1. A method for the production of a porous polymer by the polymerizationof a water-in-oil type high internal phase emulsion obtained from an oilphase containing a polymerizable monomer component and a surfactant anda water phase containing water, which method is characterized bycomprising (a) an emulsifying step for forming a water-in-oil type highinternal phase emulsion, (b) a shaping step for shaping the emulsion inthe form of a sheet or a film, and (c) a polymerizing step forpolymerizing the emulsion and having the temperatures during thecomponent steps mentioned above so controlled as to produce no changeexceeding 10° C.
 2. A method for the production of a porous polymer bythe polymerization of a water-in-oil type high internal phase emulsionobtained from an oil phase containing a polymerizable monomer componentand a surfactant and a water phase containing water, which method ischaracterized by comprising (a) a continuous emulsifying step forcontinuously forming a water-in-oil type high internal phase emulsion,(b) a continuous shaping step for continuously shaping the emulsion inthe form of a sheet or a film, and (c) a continuous polymerizing stepfor continuously polymerizing the emulsion and having the temperaturesduring the component steps mentioned above so controlled as to produceno change exceeding 10° C.
 3. A method for the production of a porouspolymer by the polymerization of a water-in-oil type high internal phaseemulsion obtained from an oil phase containing a polymerizable monomercomponent and a surfactant and a water phase containing water, whichmethod is characterized by comprising (a) a continuous emulsifying stepfor continuously forming a water-in-oil type high internal phaseemulsion, (b) a continuous shaping step for continuously shaping theemulsion in a thickness of not more than 50 mm, and (c) a continuouspolymerizing step for continuously polymerizing the emulsion and havingthe temperatures during the component steps mentioned above socontrolled as to produce no change exceeding 10° C.
 4. A method for theproduction of a porous polymer by the polymerization of a water-in-oiltype high internal phase emulsion obtained from an oil phase containinga polymerizable monomer component and a surfactant and a water phasecontaining water, which method is characterized by comprising (a) anemulsifying step for forming a water-in-oil type high internal phaseemulsion, (b) a shaping step for shaping the emulsion in the form of asheet or a film, and (c) a polymerizing step for polymerizing theemulsion and having the component steps of the process mentioned aboveto proceed invariably at a temperature of not lower than 80° C. and nothigher than 110° C.
 5. A method for the production of a porous polymerby the polymerization of a water-in-oil type high internal phaseemulsion obtained from an oil phase containing a polymerizable monomercomponent and a surfactant and a water phase containing water, whichmethod is characterized by comprising (a) a continuous emulsifying stepfor continuously forming a water-in-oil type high internal phaseemulsion, (b) a continuous shaping step for continuously shaping theemulsion in the form of a sheet or a film, and (c) a continuouspolymerizing step for continuously polymerizing the emulsion and havingthe component steps of the process mentioned above to proceed invariablyat a temperature of not lower than 80° C. and not higher than 110° C. 6.A method for the production of a porous polymer by the polymerization ofa water-in-oil type high internal phase emulsion obtained from an oilphase containing a polymerizable monomer component and a surfactant anda water phase containing water, which method is characterized bycomprising (a) a continuous emulsifying step for continuously forming awater-in-oil type high internal phase emulsion, (b) a continuous shapingstep for continuously shaping the emulsion in a thickness of not morethan 50 mm, and (c) a continuous polymerizing step for continuouslypolymerizing the emulsion and having the component steps of the processmentioned above to proceed invariably at a temperature of not lower than80° C. and not higher than 110° C.
 7. A method for the production of aporous polymer by the polymerization of a water-in-oil type highinternal phase emulsion obtained from an oil phase containing apolymerizable monomer component and a surfactant and a water phasecontaining water, which method is characterized by comprising (a) acontinuous emulsifying step for continuously forming a water-in-oil typehigh internal phase emulsion, (b) a continuous shaping step forcontinuously shaping the emulsion in a necessary shape, and (c) acontinuous polymerizing step for continuously polymerizing the emulsionand having the component steps of the process mentioned above to proceedinvariably at a temperature of not lower than 80° C. and having apolymerization initiator incorporated in the emulsion after the start of(a) the continous emulsifying step and before the completion of (b) thecontinuous shaping step.